Known helium-speech communication systems have involved transmitting the distorted speech signals (i.e. helium-speech as hereinbefore defined), via a cable, to the input of an electronic unscrambling device located at the water's surface. Prior art unscrambling devices employ digital memory means to perform a waveform time expansion in pitch synchronism with each pitch period of the speaker's voice signals and such devices have a power consumption of more than one Watt, a size in excess of 1000 cubic inches and a weight of some 17 lbs. It has thus been considered essential heretofore to locate the unscrambling device in a diving bell or at a surface station. Recently I have been involved in the development of an unscrambling device which is based upon analogue charge transfer device technology with associated complementary metal-oxide-silicon (CMOS) digital control logic which has allowed an unscrambling device to be developed which has a power consumption of 150 mW, a size of 10 cubic inches and a weight of 1/2 lb. The compact size and reduced power consumption of the new device offers operational advantages in allowing undersea use, permitting diver-borne operation of the unscrambling device.